Systematic position of the kelp endophyte Laminarionema elsbetiae (Ectocarpales sensu lato, Phaeophyceae) inferred from nuclear ribosomal DNA sequences

The recently described microscopic brown alga Laminarionema elsbetiae Kawai et Tokuyama occurs as an endophyte in Laminaria spp. in the northern hemisphere. Based on morphology, cytology, and reproductive characters it is classified in the Ectocarpales. Phylogenetic analyses of partial SSU and ITS sequences of the nuclear ribosomal DNA of Laminarionema elsbetiae and other brown algae support its placement in the clade of 'simple brown algae' (Ectocarpales sensu lato), but it is not closely related to any of the major subgroups currently recognized in the Ectocarpales sensu lato or to other kelp endophytes, which belong to the genus Laminariocolax. Comparisons include published (Adenocystis utricularis, Ectocarpus siliculosus, Gononema pectinatum, Laminariocolax tomentosoides, Scytosiphon lomentaria, 'Streblonema' sp.) as well as so far unpublished (Chordaria linearis, Dictyosiphon foeniculaceus, Myriotrichia clavaeformis, Striaria attenuata) sequences of taxa within the Ectocarpales sensu lato. The position of Laminarionema distant from other brown kelp endophytes suggests that endophytism evolved more than once in the Ectocarpales.